In oilfield exploration and production operations, prior to running any tools into a borehole, it is a common industry practice to perform a drift of the borehole. Drifting is a method used to measure and verify the inside diameter of a pipe or other cylindrical tool that may be disposed in the borehole. Typically, a cylinder or pipe of a known diameter, often referred to as a rabbit, is pulled through the pipe or cylindrical tool disposed downhole in the borehole. The outside diameter of the rabbit determines the maximum working diameter of the borehole. The drift diameter, or inner diameter, is used by well planners to determine what size tools or equipment may be disposed into the borehole. Drifting is also used to establish that the borehole is clear of obstruction, identify any particular landmarks within the borehole, and/or ensure that tools or other downhole assemblies will be able to travel through the borehole to reach specified depths.
Typically, the drift, a cylinder or pipe of a known diameter (e.g., a downhole tool), is deployed into the borehole. If the drift is obstructed, efforts are made to move the drift through the obstruction. However, if the drift will not pass the obstruction, the drift and tools must be recovered to the surface, and a drift of a smaller diameter is deployed downhole into the borehole. In some cases, multiple drift changes are required. This technique may also be used to check known landmarks within the borehole, such as nipple profiles or tubular crossovers. It is common to include landing nipples in most wells and boreholes at predetermined intervals to enable the installation of flow-control devices, such as plugs and chokes.
However, the redeployment of multiple and different drifts may be an extremely protracted sequence of events. This may result in additional costs, especially in a rig environment, as such operations may increase the time until any production is received from the well.